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The acronym for it's Still Yo Mother Fuckin' Set.

A term used bodybuilders and weightlifters alike indicating you have not completed a repetition for a particular workout.
Guy 1: My girl just called. I gotta be outta here.

Guy 2: You cannot leave just yet. ISYMFS
by jasonthecancer March 09, 2014
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May 12 Word of the Day
When someone goes to the gym and spends 90% of the time on their phones scrolling through social media
Looks like its thumb day again for Jimmy with his usual routing... 3 sets of 5 snapchat selfies and 10 sets of scrolling through facebook until exhaustion
by Gary br April 02, 2017
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2
The acronym for I Suck Your Mother's Fingers Slowly.

Term used by MILF lovers and feet fetishists. Often tattooed on different body parts to inform cougars about your preferences.
Woman: Hey is that ISYMFS on Your arm?
Boy: Yes it is.
Woman: Let's go to my house and talk about it.
by MichealQA August 13, 2019
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